Anisotropy of Static Electric Permittivity and Conductivity in Some Nematics and Smectics A

Abstract

Anisotropy of static electric permittivity and conductivity was measured for three groups of liquid crystals: (I) p-n-alkyl-p'-cyanobiphenyls (C_nH_2n+1-φ-φ-CN, n = 5,6,7,8), (II) p-p'-dialkylazoxybenzenes (C_nH_2n+1-φ-N(O) = N-φ-C_nH_2n+1, n = 5,6,7,8) and (III) p-alkyloxyphenyl-p'-alkoxybenzoates (C_nH_2n+1-O-φ-COO-φ-O-C_mH_2m+1, n = 8, m = 5; n = 8, m = 7; n = 10, m = 5; n = 11, m = 5). The nematic-smectic A phase transition for compounds of the I and II group manifests itself as a change of conductivity anisotropy sign due to a strong variation of the parallel component σ_∥ only; for compounds of the III group both components of electric conductivity and permittivity change considerably.

Keywords:

• permittivity
• conductivity
• anisotropy
• nematics
• smectics